In the bowl of an electric mixer fitted with paddle attachment, beat together pumpkin puree, brown sugar, oil, eggs, and molasses on medium speed until mixed, about 3 minutes. Scrape down sides of bowl as needed. Reduce mixer speed to low; gradually add flour mixture and mix for 30 seconds. Cover and refrigerate batter until chilled, about 30 minutes.

Bake until whoopies are deep orange and spring back when touched, about 20 minutes, rotating baking sheets halfway through. Cool completely on pans.

To make filling: In the bowl of an electric mixer fitted with paddle attachment, beat together cream cheese and butter on medium speed until fluffy, about 3 minutes. Scrape down sides of bowl as needed. Reduce mixer speed to low; add maple syrup, cinnamon, cloves, and salt, and mix for 30 seconds. Gradually add confectioners' sugar and mix for 1 minute. If filling is too soft to hold its shape, add more confectioners' sugar, 1 tablespoon at a time, until desired consistency. (Store in refrigerator, in an airtight container with plastic wrap pressed onto surface of filling, for up to 5 days.)

To fill pies: Turn half the whoopies over so they're bottom-side up. Using a pastry bag or butter knife, add a dollop (1 1/2 tablespoons) of Maple-Spice Filling onto each whoopie bottom. Top with remaining whoopies.